The prior art is replete with numerous teachings that relate to the development of environmentally friendly fuels, that is, fuels that can be used in place of traditional hydrocarbon based energy sources, and that are currently utilized in most overland vehicles. Much research has been directed, as of late, to the use of fuel cells in combination with conventional technology, in so-called “hybrid vehicles.” Notwithstanding the advances that have been made in hybrid vehicle design, no single fuel storage system has been developed that can store the fuel that is typically consumed by a fuel cell, that is hydrogen. For transportation applications, a compact light-weight, responsive and affordable hydrogen storage medium is required for overland vehicle applications. In automotive applications, it is estimated that to provide a 300 mile driving range for a typical overland vehicle, would require five to ten kilograms of usable hydrogen, depending upon the size of the vehicle. Beyond the issues of providing a suitable hydrogen storage medium, other engineering issues would also need to be addressed, such as the operating pressure and temperature that the hydrogen may be provided at, the life cycle of the hydrogen storage medium, and any requirements for hydrogen purity, which may be imposed by the fuel cell that is utilized with the overland vehicle.
Other issues, that are currently trying to be addressed for overland vehicle applications, include the methodology for replenishing the hydrogen storage medium; the types of refueling conditions to replenish the storage medium, that is, rate and time, necessary to perform this process; and the hydrogen release rate that might be achieved from such a process. Other important issues directed to safety, toxicity and system efficiency would also need careful consideration. Those familiar with the current state of the art agree that no material currently available today appears to meet all the needs for the storage of large amounts of hydrogen, which might be utilized by a hybrid vehicle. While hydrogen can be stored on an overland vehicle in a substantially pure form, such as compressed gas, or in a cryogenic liquid, these present obvious difficulties with respect to replenishing the hydrogen source once it has been depleted. While some developments have occurred, with respect to storage systems for gaseous and liquid forms of hydrogen, it is fair to say that such systems are unduly complex and still may not meet the requirements as outlined by recent information released by the U.S. Department of Energy.
In view of these difficulties, many skilled in the art have initiated research directed to chemical compounds that can store hydrogen and then later release it for use in an overland vehicle. In this regard, the storage of hydrogen and chemical compounds offers a much wider range of possibilities to meet transportation requirements. However, no single material that has been investigated to date exhibits all the necessary properties.
Finding an effective hydrogen storage medium material therefore, is one of the most difficult challenges facing designers of hybrid or electric overland vehicles. As of late, a number of investigators have considered the feasibility of synthesizing light-metal hydrides, such as borohydrides, for use in overland vehicle applications. However, as of late, the current process for synthesizing borohydrides, for example, is a lengthy solvent process, as more fully understood by a study of U.S. Pat. No. 6,670,444, the teachings of which are incorporated by reference herein. The attractiveness of utilizing a borohydride is understood by a study of the formula set forth below.NaBH4+2H2O →4H2+NaBO2+heat (300 KJ).
As seen from the formula, noted above, the spent material is sodium metaborate. The regeneration of the borohydride from the spent borates, as noted above, is a lengthy solvent process that is complex and economically unattractive.
Therefore, a method of producing a borohydride that avoids the detriments associated with the prior art practices is the subject matter of the current patent.